Orientite is a rare manganese silicate mineral typically occurring as small brown tabular crystals or radial clusters. It is highly valued by mineral collectors for its scarcity and is famously associated with manganese-rich deposits in Cuba and the Franklin Mining District.
Is this orientite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch orientite with a known reference. Orientite sits at Mohs 4.5-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous, semimetallic; pitchy to dull when included.
- 4Match the color rangeCompare against the expected color range: brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic, radial.
Often confused with
Orientite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Epidote is the harder of the two (Mohs 6-7 vs. 4.5-5); streak differs, so Orientite leaves brown, Epidote leaves grayish white; luster reads resinous, semimetallic; pitchy to dull when included on Orientite and vitreous, pearly, somewhat resinous on Epidote.
How to tell apart: Piemontite is the harder of the two (Mohs 6-6.5 vs. 4.5-5); streak differs, so Orientite leaves brown, Piemontite leaves reddish; luster reads resinous, semimetallic; pitchy to dull when included on Orientite and vitreous on Piemontite.
Often found alongside orientite
Minerals reported to co-occur with orientite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₈Mn₁₀(SiO₄)₃(Si₃O₁₀)₃(OH)₁₀(H₂O)₄
- Mohs hardness
- 4.5-5
- Density
- 3.05-3.33 g/cm³
- Streak
- Brown
- Luster
- Resinous, semimetallic; pitchy to dull when included
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic, radial
- Cleavage
- Perfect to imperfect on {001}; may be a parting
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In manganese orebodies in latite and andesite tuffs, agglomerates, and limestones (Oriente Province, Cuba); replacing calcite in fissures and lenses in basalt (Manganese Lake, Michigan, USA)
Where rockhounds find orientite
Classic worldwide localities
- Manganese Lake, Copper Harbor, Keweenaw Co., Michigan, USA
- Oriente Province, about 10 km south of Bueycito, Cuba
- Banes, north of Antilla, Cuba
- Wessels mine, near Kuruman, Cape Province, South Africa
- Cerchiara mine, near Faggiona, La Spezia, Liguria, Italy
Field-hunting tip
Where it forms: In manganese orebodies in latite and andesite tuffs, agglomerates, and limestones (Oriente Province, Cuba); replacing calcite in fissures and lenses in basalt (Manganese Lake, Michigan, USA). If you start seeing todorokite, manganite, pyrolusite in float, you are in the right ground. Typical habit: prismatic, radial. Train your eye for that shape before scanning the outcrop.
Common questions
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Find orientite on the map
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